DC to DC converters are useful in portable electronic devices such as mobile telephones, palm and laptop computers, and various other devices, which have power supplied from batteries. Portable electronic devices often are constructed from multiple circuits, each of which may operate at a voltage level that is different or even a voltage at a different polarity from other circuits. DC to DC converters can generate multiple controlled voltages from a single variable battery voltage and can accommodate a decrease in battery voltage as stored power drains, enabling improved power control and saving space through usage of a single battery instead of using multiple batteries to supply different voltages to different circuits in the device.